Multi barrel firearms are generally of a break open style. The load from firing is taken by a hinge pin and a free standing breech face. This is reasonably satisfactory in the case of shotguns since they are low pressure. Even there many attempts have been made to tie the barrels to the breech face to overcome the momentary separation of the two upon firing. Two of the most common are the dollshead and greener crossbolt. None are as substantial as needed for double rifles and rifle shotgun combinations. The resulting problems are sticking cases in the chamber from stretching and premature looseness in the action. Rifle cartridges with rims designed for break open guns for this reason are loaded to lower pressure and performance than their counterparts for rifles that lock up at the breech.